The present invention is related to the field of position encoders and their use in motion control applications.
There are many motion control applications in which an event is triggered once or multiple times at pre-determined precise positional states of a system. These events may include the activation of a device such as a laser, camera, radar, sonar, x-ray, etc. The motion of a stage relative to the device is controlled by a controller, and a position encoder is used to detect relative position and provide position feedback information to the controller. These systems may employ trigger generation electronics to create a digital signal that triggers the event(s) when the stage has particular position(s). The trigger generation electronics operate in response to signals from the controller, which in turn are generated based on the position feedback information from the encoder. The trigger generation electronics may be packaged separately from the controller, or in some cases together with the controller.
With the current technology, the controller deciphers position data from the encoder and outputs corresponding position data to the trigger generation electronics, which uses the position data to generate trigger(s) at desired position(s). There can be significant delay (or latency) between the detection of a position by the encoder and the generating of a trigger signal by the trigger generation electronics. This delay can contribute to inaccuracy in operation, because the stage continues to move during the response time of the controller and trigger generation electronics and thus the resulting event (e.g., firing of a laser) does not occur precisely at the desired position. Additionally, trigger outputs may not be accurately spaced due to “jitter” (variability in the response time relative to motion speed), so that the resulting events are irregularly spaced.